Insects And Science Ideas

Specially designed ditches assume water-cleansing role OMSI has a new kind of parking lot for Science Project Ideas. And like a lot of the other innovations incorporated into the new complex, this one turns out to be a science project.

You won't find fish or frogs in the scooped-out, gravel-lined ditches where you'd usually expect to find a parkway covered with barkdust in Science Project Ideas. But there are bullrushes and cattails and river rock and lots of native plants. Straggly salal struggles to get a foothold near the top of the ditch, while new maple trees reach their branches to the sky.

It looks like a wetland, smells like a wetland and sounds like a wetland. And designers hope the ditches do the job that wetlands perform all over the world: clean the water that passes through them.

In the bottom of the ditches, wooden baffles, or weirs, are built at about 20-foot intervals to hold back water, allowing the rainwater runoff from the 800-space parking lot to percolate through the rock and gravel and clay soil, thereby cleansing itself of oil, grease and the other junk cars leave behind.

The city of Portland's Bureau of Environmental Services asked the Oregon Museum of Science and Industry to build the wetlands/biofiltration system as a demonstration project, said Dean Ivey, the museum's facility services director.

''The city has a problem because every time it rains into a parking lot, the water washes across and collects all the oil, grease, gasoline and petroleum byproducts left behind and dumps it into the storm drains and then into the river,'' Ivey said.

Scientists only recently have discovered how vital wetlands are as natural filters for surface and ground water. The parking lot's ''wetland cells'' system at the new complex is an offshoot of that knowledge.

Ivey said the city was trying to find ways to cut pollutants that go into the river. The owners of parking lots are charged a drainage fee based on the size of any paved area that is impervious to rainwater.

OMSI's fee will be reduced, and if the wetlands/biofiltration system works, it's likely the city will encourage other commercial and industrial parking lot owners to install the systems in existing and new parking lots.

In time, the small native plants will grow, giving the five ditches in the three parking lots a more natural look that will attract birds and other wildlife. Ivey said the No. 1 question people ask is if the wetlands will be a breeding ground for mosquitoes.

"Quite frankly, if you live anywhere along this river, you're going to have mosquitoes,'' Ivey said. "We're not that far from Oaks Bottom. The few mosquitoes we'll create here will be nothing compared to what it normally is anyway.''